1. Field of the Invention
The present invention relates to a magnetic recording medium of ferromagnetic metal and a sliding member such as a magnetic head having a protection film and a manufacturing method thereof.
2. Description of the Prior Art
A magnetic recording medium of ferromagnetic metal is formed by forming Co, Ni or Fe or an alloy including Co, Ni or Fe as a main component with use of vacuum deposition, sputtering, ion plating or the like, on a substrate of polymer film of polyester, polyimide or the like or of nonmagnetic metal. Such a type of magnetic recording medium can increase the recording density precipitously compared with a magnetic recording medium of coating type.
In order to increase the recording density of the magnetic recording medium of ferromagnetic metal, it is important to decrease the defects in the magnetic layer for recording and reproduction as small as possible and to decrease the spacing loss between the magnetic head and the magnetic recording medium as small as possible. Further, it is also necessary for a magnetic recording medium of ferromagnetic metal to have an endurance property.
In order to satisfy these conditions, a protection film and a lubricant layer are known to be provided on the magnetic layer of the magnetic recording medium after the magnetic layer is formed (for example Japanese Patent laid open Publication 2-158909/1990). Further, an oxide layer and a lubricant layer are formed after the formation of the magnetic layer (Japanese Patent laid open Publication 3-113825/1991), and a magnetic disk is subjected to the plasma processing with inert gas such as nitrogen after a lubricant layer of fluoroether is formed on a protection film of carbon (U.S. Pat. No. 4,960,609).
However, in the above-mentioned magnetic recording medium wherein a lubricant layer is formed on a protection film, the bond between the protection film and the lubricant is insufficient. Then, when the magnetic recording medium is used practically in a video cassette recorder, the lubricant layer is scratched by the head and the head clogging occurs eventually. On the other hand, in the above-mentioned method of providing an oxidation layer on a protection film and a lubricant layer on a protection film and in the above-mentioned method of plasma processing with inert gas after a lubricant layer is formed on a protection film, defects such as pin holes are generated in the protection film itself due to ion damages or the like, and this deteriorates the corrosion resistance.
A sliding member such as a magnetic head, a fixing guide to guide a tape in a video cassette recorder or a drum for recording and reproduction is required to maintain the abrasion resistance and the low friction characteristic for a long time. As to a magnetic head, especially a metal-in-gap head, a head of layered type and a head of thin film type which expose a different kind of material on the sliding plane of recording medium, the sliding with a different material occurs at the sliding plane, so that a material of lower hardness is abrased and the spacing with the medium increases near the gap of the head. Then, the magnetization of the medium becomes insufficient on recording and the magnetization signal of the medium is not read sufficiently on reproduction. Thus, the output decreases largely.
In order to satisfy these properties, a diamond-like carbon film or a hard carbon film is used as a protection film on a metallic base (for example, a drum for magnetic recording and reproduction disclosed in Japanese Patent laid open Publication 2-125456/1980, and a sliding member disclosed in Japanese Patent laid open Publication 2-158690/1990).
However, in such a sliding member, though the abrasion resistance for a short time can be improved, not only a component sliding counter to the sliding member is abrased, but also the friction coefficient increases and the component itself is abrased rapidly after a certain time passes so that the function as a sliding member is lost.